1. Field of the Invention
The present invention relates to an active matrix display apparatus and, more particularly, to a display apparatus including an active matrix display panel having light-emitting elements such as organic electroluminescence elements.
2. Description of the Related Art
A matrix type display including a light-emitting panel is being widely developed. The light-emitting panel includes a plurality of light-emitting elements arranged in a matrix configuration. The light-emitting elements for use in such display panels include, for example, an electroluminescence (EL) element which employs an organic material as a light-emitting layer. The light-emitting luminance can be controlled by a current which flows through in the organic EL element. The light-emitting display panels using the organic EL elements may be classified into a simple matrix display panel and an active matrix display panel. The organic EL elements are merely arranged in a matrix configuration in the simple matrix light-emitting panel. On the other hand, a driving device including a transistor is added to each of the organic EL elements arranged in a matrix configuration in the active matrix light-emitting panel. The active matrix light-emitting panel has advantages such that electric power consumption is smaller and an amount of crosstalk between pixels is smaller as compared with those of the simple matrix light-emitting panels and the like are suitable as a display of a large screen or a high precision display.
FIG. 1 illustrates an example of a circuit configuration corresponding to a pixel 10 of an active matrix display panel according to the prior art.
Referring to FIG. 1, a gate G of a FET (Field Effect Transistor) 11 (an address selection transistor) is connected to an address scan electrode (scan line) through which address signals are supplied. A drain D of the FET 11 is connected to a data electrode (data line) through which a data signal is supplied. A source S of the FET 11 is connected to a gate G of a FET 12 (a drive transistor) as well as to one terminal of a capacitor 13. A source S of the FET 12 is connected to a common anode 16 in conjunction with the other terminal of the capacitor 13. The drain D of the FET 12 is connected to the anode of an organic EL element 15, and a cathode of the organic EL element 15 is connected to a common cathode 17.
As illustrated in FIG. 2, the common anode 16 and the common cathode 17 to which the cathode of each organic EL element 15 is connected are connected to a voltage source 18 for supplying power.
A light emission control operation of the circuit is described hereinbelow. Referring to FIG. 1, an ON voltage supplied to the gate G of the FET 11 causes a current corresponding to a data voltage supplied to the source S to flow from the source S to the drain D. When the gate G of the FET 11 is at an OFF voltage, the FET 11 is in a so-called cut-off state making the drain D of the FET 11 open. Therefore, the capacitor 13 is charged while the gate G of the FET 11 is kept at the ON voltage to supply the voltage of the capacitor 13 to the gate G of the FET 12. Then, a current caused by the gate and the source voltage flows through the organic EL element 15 from the source S to the drain D in the FET 12 to allow the organic EL element 15 to emit light. Moreover, when the gate G of the FET 11 is at the OFF voltage, the FET 11 is made open. Accordingly, the voltage of the gate G in the FET 12 is held with the charge accumulated in the capacitor 13 to sustain the drive current until the next scan and thus the light emission of the organic EL element 15. Incidentally, the same operation as the foregoing can be obtained without the capacitor 13, since gate input capacitance is available between the gate G and the source S of the FET 12.
The circuit corresponding to a pixel of a display panel for controlling light emission by active matrix addressing is configured as described above, and the light emission of the pixel is sustained when the organic EL element 15 of the pixel is driven.
As described above, the light emission of each light-emitting element in an active matrix display panel was controlled by means of a drive circuit that contained drive elements such as FETs.
However, the active matrix display apparatus according to the prior art provided only a limited degree of flexibility for the control of the light-emitting elements since the light emission of each light-emitting element was controlled only by means of a drive circuit.
It is therefore an object of the present invention to overcome the problem described above and to provide an active matrix display apparatus having a high degree of flexibility in controlling light-emitting elements.
According to the present invention, there is provided an active matrix display apparatus, which comprises a display panel including a plurality of light-emitting elements arranged at intersections of scan lines and data lines arranged in a matrix configuration, a drive circuit for driving each of the plurality of light-emitting elements, and a conductive portion connected to one terminal of each of the plurality of light-emitting elements, a display controller for controlling the drive circuit in response to an input video signal, and a power supply for supplying electric power to the plurality of light-emitting elements via the conductive portion, wherein the conductive portion includes a plurality of strip electrodes each provided for at least one of the scan lines or the data lines and electrically isolated from one another, and the power supply includes a switch circuit for selectively connecting each of the plurality of strip electrodes to the power supply.
According to another aspect of the present invention, the apparatus further comprises, a reverse bias voltage generating circuit for generating reverse bias voltage in a direction opposite to a voltage applied to the light-emitting elements when emitting light, and a reverse bias voltage applying circuit for selectively applying the reverse bias voltage to the plurality of light-emitting elements via the plurality of strip electrodes.
According to another aspect of the present invention, the display controller includes a timer and controls the switch circuits in response to an output of the timer to selectively connect each of the plurality of strip electrodes to the power supply.
According to the present invention, there is provided an active matrix display panel, which comprises a plurality of light-emitting elements arranged at intersections of scan lines and data lines arranged in a matrix configuration, a drive circuit for driving each of the plurality of light-emitting elements, and a conductive portion connected to one terminal of each of the plurality of light-emitting elements, wherein the conductive portion includes a plurality of strip electrodes each provided for at least one of the scan lines or the data lines and electrically isolated from one another.